I've been on Amantadine, eldepryl and benadryl since I was DXed several years ago. Because of heart problems my doctor doesn't want to put me on Sinemet until we arrive at a "have to" stage. Although each person's response to various drugs are different, I think the Amantadine has been very effective. Some of the side effects are possible hallucinations, skin rashes, insomnia, etc. The only bad effect I had was the skin rash, which seems to be common. No one really understands why this drug is effect, but it reduces rigidity, tremor and impaired movement associated with PD. My base intake is 3 100mg pills per day, although I vary it according to need. If you take more than 500, something bad is suppose to happen, like your toes blow up, although I've taken 600 mg a day when I wasn't doing too well.